In the early phases of embeddedreal-timesystems development, design decisions are made with large consequences on the quality of the resulting product. At the same time, only limited information is available about k...
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ISBN:
(纸本)0769523463
In the early phases of embeddedreal-timesystems development, design decisions are made with large consequences on the quality of the resulting product. At the same time, only limited information is available about key attributes, which makes it difficult to get correct decisions. In this paper, it is studied how to include uncertainty in the information in early phases and to handle the risks involved. Using Monte Carlo simulation, the uncertainties are evaluated based on estimations of basic parameters. the technique is applied to schedulability analysis, and it is shown that the results can be counter-intuitive, and thus that current design practice can lead to higher risk than assumed by the designers.
When real-timeembedded system software needs to be upgraded, it will be more dependable if the new software is sufficiently tested on the actual deployment platform. the challenge is to provide a safeguard for protec...
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ISBN:
(纸本)0769523463
When real-timeembedded system software needs to be upgraded, it will be more dependable if the new software is sufficiently tested on the actual deployment platform. the challenge is to provide a safeguard for protecting the normal operations from faulty upgrades. However, the safeguard must be not only efficient but also able to be added and taken away as needed without shutting down the normal operations. We have developed an architecture based an Simplex Architecture and Process Resurrection and have applied it to the inverted pendulum control system. the measurements show that the overhead is small and justifiable.
Taking dynamic branch prediction into account in WCET determination turns out to be complex, particularly because of the possible interferences between branches. In this paper we argue the case for using static instea...
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ISBN:
(纸本)0769523463
Taking dynamic branch prediction into account in WCET determination turns out to be complex, particularly because of the possible interferences between branches. In this paper we argue the case for using static instead of dynamic branch prediction: the aliasing problem is swept away and, in many cases, the estimated worst-case numbers of branch mispredictions are reduced We propose a method to predict each branch at compile time. Experimental results show how effective this approach can be.
this paper presents an implementation of feedback control strategy on distributed static scheduling. the static schedule is created taking into account the average execution times of the tasks. Feedback control algori...
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ISBN:
(纸本)0769523463
this paper presents an implementation of feedback control strategy on distributed static scheduling. the static schedule is created taking into account the average execution times of the tasks. Feedback control algorithm handles the unestimated dynamic behaviors in the system and keeps the performance at a desired level. the approach of feedback control supporting static scheduling yields more flexible scheduling, low scheduling overhead and better resource utilization while preserving the real-time constraints.
Building real-timeapplications on 802.11 wireless networks is challenging because the medium access protocol is distributed and nodes contend for the channel nondeterministically. So far all attempts at providing rea...
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ISBN:
(纸本)0769523463
Building real-timeapplications on 802.11 wireless networks is challenging because the medium access protocol is distributed and nodes contend for the channel nondeterministically. So far all attempts at providing real-time services in 802.11 require restrictive traffic assumptions such as periodicity. In this paper we describe distributed admission control, a modification to 802.11 that, when used with distributed prioritization, provides real-time guarantees for aperiodic packets. We show that barring external errors such as interference on the channel or incorrect priority scheduling this protocol guarantees deadlines will be met.
We present 2V-DBP-SNAP an algorithm that allows hard real-time tasks in an embeddedreal-time control system to read a snapshot of a number of data elements in a real-time database. Furthermore, 2V-DBP-SNAP allows the...
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ISBN:
(纸本)0769523463
We present 2V-DBP-SNAP an algorithm that allows hard real-time tasks in an embeddedreal-time control system to read a snapshot of a number of data elements in a real-time database. Furthermore, 2V-DBP-SNAP allows these data elements to be shared with soft real-time tasks, which access them using a database query language, and with other hard real-time tasks that use database pointers. 2V-DBP-SNAP allows temporal behavior and memory consumption to be accurately predicted. Introducing snapshot transactions is beneficial for embedded control-systems, such as for engine control in an automotive system, since a snapshot of the state of the environment can be collected, e.g., the state of all cylinders in the engine. 2V-DBP-SNAP is lightweight and predictable, both with respect to computational and memory overhead, and is therefore highly suited for resource constrained systems.
We present a SAT-based approach to the task and message allocation problem of distributed real-timesystems. in contrast to the heuristic approaches usually applied to this problem, our approach is guaranteed to find ...
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ISBN:
(纸本)0769523463
We present a SAT-based approach to the task and message allocation problem of distributed real-timesystems. in contrast to the heuristic approaches usually applied to this problem, our approach is guaranteed to find an optimal allocation for realistic task systems running on complex target architectures. Our method is based on the transformation of such scheduling problems into nonlinear integer optimization problems. the core of the numerical optimization procedure we use to discharge those problems is a solver for arbitrary Boolean combinations of integer constraints. Optimal solutions are obtained by imposing a binary search scheme on top of that solver Experiments show the applicability of our approach to industrial-size task systems.
Under limited parallelism, processes competing for a single processor may issue at any time operations on remote co-processors, during which the processor is not idled but granted to other ready processes instead. We ...
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ISBN:
(纸本)0769523463
Under limited parallelism, processes competing for a single processor may issue at any time operations on remote co-processors, during which the processor is not idled but granted to other ready processes instead. We reduce the pessimism in existing Worst-case Response time (WCRT) analysis for such systems by examining temporal patterns of local/remote execution. We extend to multi-CPU variants of the model and offer a WCRT-based feasibility test for Symmetric Multiprocessor (SMP) systems.
In recent years, there has been much research on ubiquitous computing, including context aware computingthat is an important field in ubiquitous computing. the primary focus of this paper is on context modeling. We s...
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ISBN:
(纸本)0769523463
In recent years, there has been much research on ubiquitous computing, including context aware computingthat is an important field in ubiquitous computing. the primary focus of this paper is on context modeling. We study the characteristics of context and so the requirements on the modeling. Besides, we also take into account the development requirements of next generation context-aware application. We study the context modeling approaches of some famous existing projects and find that few models meet all these requirements. In this paper, we propose a comprehensive model, which meets these requirements. We implement this model in a middleware called Scudware.
Large-scale distributed systems, such as ubiquitous computing environments, require a service delivery mechanism in order to keep track of the vast set of services offered and make them available to interested clients...
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ISBN:
(纸本)0769523463
Large-scale distributed systems, such as ubiquitous computing environments, require a service delivery mechanism in order to keep track of the vast set of services offered and make them available to interested clients. the amount of services and clients, their context, and loose coupling between them makes service delivery in ubiquitous environments different from other systems. this paper presents a solution to overcome these issues by utilizing the underlying ontology and semantics for service lookup. Access control over context data is also considered by specifying dynamic policies at the system and service level.(1)
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